Secure Printed Memory

ABSTRACT

Copyright protection for printed memory is more difficult than writable memory. Accordingly, the present invention discloses a secure printed memory. Its printed-memory module stores the same content data for all devices in a same family; its writable-memory module stores different encryption keys for different devices in the same family. Because different devices in the same family are encrypted with different keys, compromising a single device does not compromise other devices in the family.

CROSS-REFERENCE TO RELATED APPLICATION

This is a continuation-in-part of application entitled “SecureThree-Dimensional Mask-Programmed Read-Only Memory”, Ser. No.13/951,462, filed Jul. 26, 2013, which is a continuation of applicationentitled “Secure Three-Dimensional Mask-Programmed Read-Only Memory”,Ser. No. 13/027,274, filed Feb. 15, 2011.

BACKGROUND

1. Technical Field of the Invention

The present invention relates to the field of printed memory, and moreparticularly to semiconductor printed memory.

2. Prior Arts

Printed memory refers to a read-only memory (ROM) whose data areprinted. It comprises at least a data-coding layer whose physicalpattern represents data. This physical pattern, also referred to as adata-pattern, is transferred from at least a data-template (also knownas data-master, data-mask or others) using a printing method during amanufacturing process. Hereinafter, all copies of the printed memorywhose data are printed from a same set of data-template(s) arecollectively referred to as a printed-memory family.

Printed memory is widely used in optical storage and semiconductormemory. In optical storage, a printed memory is known as an opticalprinted memory. It is primarily optical disc, e.g., CD, DVD and BD(Blu-ray). In semiconductor memory, a printed memory is known as asemiconductor printed memory. It primarily includes mask-programmedread-only memory (mask-ROM) and imprinted memory (whose content data areprinted into the data-coding layer using a nano-imprint method,referring to U.S. patent application Ser. No. 13/602,095, filed Aug. 31,2012). One notable semiconductor printed memory is three-dimensionalprinted memory (3D-P, shown in FIG. 6, also referring to U.S. patentapplication Ser. No. 13/570,216, “Three-Dimensional Printed Memory”,filed Aug. 8, 2012).

As a permanent storage, printed memory is a preferred medium forpublication. For copyright protection, the prior-art printed memoryencrypts its content by encrypting the data on the data-template(s). Fora printed-memory family 100 whose devices (100 a, 100 b . . . 100 z)store the same contents, because all of these devices use a same set ofdata-template(s) to print content data, they use a same set ofencryption key(s) (k_(a) for 100 a, k_(b) for 100 b . . . k_(z) for 100z, with k_(a)=k_(b)= . . . =k_(z)) (FIG. 1). Compromising a singledevice (e.g., 100 a) would compromise other devices in the same family100. In contrast, a writable memory has a better copyright protection.For a writable-memory family 200 whose devices (200 a, 200 b . . . 200z) store the same contents, because different devices may use differentsets of encryption keys (k*_(a) for 200 a, k*_(b) for 200 b . . . k*_(z)for 200 z, with k*_(a)≠k*_(b)≠ . . . ≠k*_(z)) (FIG. 2), compromising onedevice does not compromise other devices in the family 200.

OBJECTS AND ADVANTAGES

It is a principle object of the present invention to improve copyrightprotection for semiconductor printed memory.

It is a further object of the present invention to protect the contentsof other devices in the same family when a single device is compromised.

In accordance with these and other objects of the present invention, asecure printed memory is disclosed.

SUMMARY OF THE INVENTION

Semiconductor printed memory has a better copyright protection thanoptical printed memory. Because an optical printed memory is astandalone device and cannot be integrated with an encryption circuitcomprising variable encryption keys, its copyright protection islimited. On the other hand, because a semiconductor printed memory canbe integrated with an encryption circuit comprising variable encryptionkeys, its copyright protection can be enhanced to a level like awritable memory, i.e., each device uses a different set of encryptionkey(s). Accordingly, the present invention discloses a secure printedmemory. It comprises a semiconductor printed-memory module, asemiconductor writable-memory module and an encryption-circuit module.The semiconductor printed-memory module stores content data, which aresame for all devices in a family. The semiconductor writable-memorymodule stores variable encryption key(s), which may be different fordifferent devices in the family. The encryption-circuit module encryptsa selected content(s) in the printed-memory module with a selectedkey(s) from the writable-memory module. Because different devices in afamily may use different encryption keys, compromising a single devicedoes not compromise other devices in the same family.

To further improve copyright protection, all components of a secureprinted memory, including the semiconductor printed-memory module, thesemiconductor writable-memory module and the encryption-circuit module,are preferably integrated into a single chip, or a single protectivepackage. This can prevent the intermediate signals from thesemiconductor printed-memory module and the semiconductorwritable-memory module from being exposed to the external worlds.

To further protect encryption keys, a secure three-dimensional printedmemory (3D-P) is disclosed. Its semiconductor printed-memory module(i.e., 3D-P module) comprises a plurality of monolithically stackedprinted-memory levels. Because the 3D-P module covers the semiconductorwritable-memory module carrying the encryption keys, uncovering theencryption keys requires removal of the 3D-P module, or the contentdata. This defies the whole purpose of pirating.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a prior-art printed-memory family and the keys usedby respective devices;

FIG. 2 illustrates a prior-art writable-memory family and the keys usedby respective devices;

FIG. 3 illustrates a secure printed-memory family and the keys used byrespective devices;

FIG. 4 is a block diagram of a preferred secure printed memory;

FIG. 5 is a block diagram of another preferred secure printed memory;

FIG. 6 is a cross-sectional view of a preferred secure 3D-P;

FIG. 7 is a top view of the preferred secure 3D-P, showing the 3D-Pmodule and its peripheral circuit;

FIGS. 8A-8C illustrate three examples of the secure 3D-P of FIG. 7 withthe 3D-P module not shown, revealing the substrate;

FIG. 9 is a cross-sectional view of a preferred secure printed-memorypackage;

FIGS. 10AA-10BB illustrate two cases of the secure printed-memorypackage of FIG. 9.

It should be noted that all the drawings are schematic and not drawn toscale. Relative dimensions and proportions of parts of the devicestructures in the figures have been shown exaggerated or reduced in sizefor the sake of clarity and convenience in the drawings. The samereference symbols are generally used to refer to corresponding orsimilar features in the different embodiments.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Those of ordinary skills in the art will realize that the followingdescription of the present invention is illustrative only and is notintended to be in any way limiting. Other embodiments of the inventionwill readily suggest themselves to such skilled persons from anexamination of the within disclosure.

Referring to FIG. 3, a family 300 of secure printed memory is disclosed.It includes a plurality of devices 300 a, 300 b . . . 300 z. Beingprinted from the same set of data-template(s), these devices store thesame contents. However, by integrating with an encryption circuitcomprising variable encryption keys, different devices 300 a, 300 b . .. 300 z may use different encryption keys K_(a), K_(b) . . . K_(z) (withK_(a)≠K_(b)≠ . . . K_(z)). This level of this copyright protection issame as that of a writable memory (FIG. 2), and is much stronger thanthat of the prior-art printed memory (FIG. 1).

FIG. 4 is a block diagram a preferred secure printed memory 50. Itcomprises a semiconductor printed-memory module 20, a semiconductorwritable-memory module 30 and an encryption-circuit module 40. Thesemiconductor printed-memory module 20 stores contents, including butnot limited to: visual contents (e.g., photos, digital maps, movies,television programs, videos, video games), audio contents (e.g., music,songs, audio books), textual contents (e.g., electronic books, orebooks), software and/or their libraries. Being hard-coded, thesecontent data are same for all devices 300 a, 300 b . . . 300 z in theprinted-memory family 300.

The semiconductor writable-memory module 30 stores variable encryptionkey(s) 32. It is a non-volatile memory that can be written usingoptical, electrical, or magnetic programming method. Key(s) can bewritten during or after manufacturing. Examples of semiconductorwritable-memory module include laser-programmable read-only memory(LP-ROM), electrically-programmable read-only memory (EP-ROM), andothers. Being soft-coded, key(s) 32 may be different for differentdevices 300 a, 300 b . . . 300 z in a same family 300.

The encryption-circuit module 40 encrypts selected content data 22 fromthe semiconductor printed-memory module 20 with a selected key 32 fromthe semiconductor writable-memory module 30 in such a way that theread-out 42 of the secure semiconductor printed-memory 50 is encryptedwith different keys for different devices. Various encryption algorithmsmay be employed, e.g., PGP, AES, 3DES, Blowfish. The encryption-circuitmodule 40 could also be a data scrambler, which re-arranges content data22 according to a pattern defined by the key 32. In the mean time, toimprove the efficiency of the encryption-circuit module 40, the contentdata may be only partially encrypted.

FIG. 5 is a block diagram another preferred secure printed memory 50,which provides file-dependent encryption and time-variant encryption. Itfurther comprises a key-selection logic 34. The semiconductorprinted-memory module 20 stores a plurality of data files (22 a, 22 b .. . ), while the semiconductor writable-memory module 30 stores aplurality of keys (32 a, 32 b, 32 c . . . ). The key-selection logic 34selects key(s) based on an input 36 such as file address, time or otherinformation.

For file-dependent encryption, different data files are encrypted bydifferent keys. For example, the data file 22 a is encrypted by the key32 a, while the data file 22 b is encrypted by the key 32 b . . . . Onthe other hand, for time-variant encryption, data files are encrypted bydifferent keys during different time periods. For example, the data file22 a is encrypted by the key 32 a during a first time period, andencrypted by the key 32 c during a second time period . . . . All thesefeatures add complexity to breaking into secure printed memory. Besidesthese techniques, other copyright-enhancing techniques can also be used.For example, different portions of the data file can be encrypted bydifferent keys.

To further improve copyright protection, all components of a secureprinted memory 50, including the semiconductor printed-memory module 20,the semiconductor writable-memory module 30 and the encryption-circuitmodule 40, are preferably integrated in a single chip (FIGS. 6-8C), orin a single protective package (FIG. 9-10BB). Because all datacommunications are located inside the chip (or, the protective package),the intermediate signals 22, 32 from the semiconductor printed-memorymodule 20 and the semiconductor writable-memory module 30 are notexposed to the external world and are difficult to be tampered with.

Referring now to FIG. 6, a preferred secure 3D-P 50 is disclosed. Itcomprises a 3D-P module 20, a semiconductor writable-memory module (i.e.a writable memory) 30 and an encryption-circuit module (i.e., anencryption circuit) 40. The 3D-P module 20 is a monolithic semiconductormemory. It is formed on a semiconductor substrate 00 includingtransistors 33 and interconnects. The 3D-P module 20 comprises aplurality of printed-memory levels (20A, 20B . . . ), which arevertically stacked above one another and coupled to the semiconductorsubstrate 00 through contact vias (1 av . . . ). Each printed-memorylevel 20 further comprises a plurality of address lines (1 a . . . ; 2a-2 d . . . ) and memory cells (8 aa-8 da . . . ) at the intersectionbetween address-selection lines. The data stored in memory cells (8 aa-8da . . . ) are printed during manufacturing. The printing methodsinclude photolithography (through at least a data-mask) and imprint(with at least a data-template, referring to U.S. patent applicationSer. No. 13/602,095, “Imprinted Memory”, filed Aug. 31, 2012). Moredetails on 3D-P can be found in U.S. patent application Ser. No.13/570,216, “Three-Dimensional Printed Memory”, filed Aug. 8, 2012.

The writable memory 30 and the encryption circuit 40 are preferablyformed below the 3D-P module 20. In this preferred embodiment, thewritable memory 30 is a laser-programmable read-only-memory (LP-ROM). Itcomprises a laser-programmable fuse 35 and can be programmed duringmanufacturing, e.g., before the 3D-P module 20 are formed. By shining alaser beam onto the fuse 35, a gap 37 can be formed in the fuse 35.Existence or absence of the gap 37 indicates the digital state of theLP-ROM cell. Among all types of writable memory 30, LP-ROM isparticularly advantageous because it does not require high-voltageprogramming transistor and incurs minimum process change. Note that,although it is programmed by changing the physical structure of thefuse, LP-ROM is still considered as “soft-coded” because different keyscan be programmed into different LP-ROM's.

FIG. 7 is a top view of the preferred secure 3D-P 50, showing the 3D-Pmodule 20 (shaded areas) and its associated peripheral circuit 28. FIGS.7A-7C illustrate three cases of the secure 3D-P chip with 3D-P module 20not shown, revealing the substrate 00. In FIG. 8A, the writable memory30 and the encryption circuit 40 are formed on the substrate 00 butoutside the 3D-P module 20. In FIG. 8B, the writable memory 30 is formedunderneath the 3D-P module 20. The encryption circuit 40 is formedoutside the 3D-P module 20 and can be shared. In FIG. 8C, both thewritable memory 30 and the encryption circuit 40 are formed underneaththe 3D-P module 20. Forming at least a portion of the writable memory 30underneath the 3D-P module 20 (as in FIGS. 7B-7C) is advantageousbecause uncovering the encryption keys carried by the writable memory 30requires removal of the 3D-P module 20, which stores the content data.This defies the whole purpose of pirating. Note that FIGS. 7-8C aremerely representative and are not intended to indicate any actuallayout. Layout is a design choice and many configurations are possible.

FIG. 9 is a cross-sectional view of a preferred secure printed-memorypackage 50. In this preferred embodiment, the semiconductorprinted-memory module 20, the semiconductor writable-memory module 30and the encryption-circuit module 40 are integrated into a singleprotective package 50. It comprises at least one printed-memory chip52A, 52B . . . and a support chip 54. All of these chips (52A, 52B . . ., 54) are preferably stacked above one another and coupled to each otherthrough bonding wires 56, then placed in a secure housing 58 filled withprotective materials 59 such as molding compound. Because theintermediate signals from the semiconductor printed-memory module 20 andthe semiconductor writable-memory module 30 are not exposed to theexternal world and are difficult to be tampered with, this preferredembodiment provides strong copyright protection.

FIGS. 10AA-10BB illustrate two cases of the secure 3D-P package 50 ofFIG. 9. In the case of FIGS. 10AA-10AB, the 3D-P chip 52A comprises atleast one 3D-P array 20 x (shaded area) and at least one writable-memoryarray 30 x. The writable-memory array 30 x is located underneath the3D-P array 20 x (FIG. 10AA). In the meantime, the support chip 54comprises the encryption circuit 40 (FIG. 10AB). In the case of FIGS.10BA-10BB, the 3D-P chip 52A comprises at least one 3D-P array 20 y(FIG. 10BA), while the support chip 54 comprises at least onewritable-memory array 30 y and the encryption circuit 40 (FIG. 10BB).

While illustrative embodiments have been shown and described, it wouldbe apparent to those skilled in the art that may more modifications thanthat have been mentioned above are possible without departing from theinventive concepts set forth therein. The invention, therefore, is notto be limited except in the spirit of the appended claims.

What is claimed is:
 1. A secure printed memory in a secureprinted-memory family, comprising: a semiconductor printed-memory modulefor storing content data, wherein said content data are same for alldevices in said secure printed-memory family; a semiconductorwritable-memory module for storing at least a key, wherein said key isdifferent for different devices in said secure printed-memory family;and an encryption-circuit module for encrypting said content data insaid semiconductor printed-memory module with said key from saidsemiconductor writable-memory module.
 2. The secure printed memoryaccording to claim 1, wherein said semiconductor printed-memory module,said semiconductor writable-memory module and said encryption-circuitmodule are located on a single chip.
 3. The secure printed memoryaccording to claim 1, wherein said semiconductor printed-memory module,said semiconductor writable-memory module and said encryption-circuitmodule are located in a protective package.
 4. The secure printed memoryaccording to claim 1, wherein said semiconductor printed-memory moduleis a mask-programmed read-only memory (mask-ROM).
 5. The secure printedmemory according to claim 1, wherein said semiconductor printed-memorymodule is an imprinted memory.
 6. The secure printed memory according toclaim 1, wherein said key in said semiconductor writable-memory moduleis written using optical, electrical or magnetic programming method. 7.The secure printed memory according to claim 6, wherein saidsemiconductor writable-memory module is a laser-programmable read-onlymemory (LP-ROM).
 8. The secure printed memory according to claim 6,where said semiconductor writable-memory module is anelectrically-writable read-only memory (EP-ROM).
 9. The secure printedmemory according to claim 1, wherein said semiconductor writable-memorymodule stores a plurality of keys and said secure printed memory furthercomprises a key-selection logic for selecting at least a key from saidplurality of keys.
 10. The secure printed memory according to claim 9,wherein said encryption-circuit module provides file-dependentencryption and said key-selection logic selects said key base on file.11. The secure printed memory according to claim 9, wherein saidencryption-circuit module provides time-variant encryption and saidkey-selection logic selects said key base on time.
 12. A securethree-dimensional printed memory (3D-P) in a secure 3D-P family,comprising: a semiconductor substrate containing transistors; aplurality of printed-memory levels stacked above and coupled to saidsubstrate, said printed-memory levels storing content data, wherein saidcontent data are same for all devices in said 3D-P family; a writablememory between said printed-memory levels and said substrate for storingat least a key, wherein said key is different for different devices insaid 3D-P family; and an encryption circuit for encrypting said contentdata in said printed-memory levels with said key from said writablememory.
 13. The secure 3D-P according to claim 12, wherein said 3D-P isa three-dimensional mask-programmed read-only memory (3D-MPROM).
 14. Thesecure 3D-P according to claim 12, wherein said 3D-P is athree-dimensional imprinted memory.
 15. The secure 3D-P according toclaim 12, wherein said key in said writable memory is written usingoptical, electrical or magnetic programming method.
 16. The secure 3D-Paccording to claim 15, wherein said key in said writable memory is alaser-programmable read-only memory (LP-ROM).
 17. The secure 3D-Paccording to claim 15, wherein said key in said writable memory is aelectrically-programmable read-only memory (EP-ROM).
 18. The secure 3D-Paccording to claim 15, wherein said writable memory stores a pluralityof keys and said secure 3D-P further comprises a key-selection logic forselecting at least a key from said writable memory.
 19. The secure 3D-Paccording to claim 18, wherein said encryption circuit providesfile-dependent encryption and said key-selection logic selects said keybase on file.
 20. The secure 3D-P according to claim 18, wherein saidencryption circuit provides time-variant encryption and saidkey-selection logic selects said key base on time.